Ferroelectric liquid crystal compounds having perfluoroether terminal portions

ABSTRACT

Fluorine-containing liquid crystal compounds are provided. The compounds comprise a fluorocarbon terminal portion having at least one catenary ether oxygen and a hydrocarbon terminal portion, the terminal portion being connected by a central core, the compounds having smectic mesophases or having latent smectic mesophases.

FIELD OF THE INVENTION

This invention relates to fluorinated achiral smectic liquid crystalcompounds. These compounds and mixtures of liquid crystal materialscontaining these compounds are useful in a variety of electroopticaldisplays.

BACKGROUND OF THE INVENTION

Devices employing liquid crystals have found use in a variety ofelectrooptical applications, in particular those which require compact,energy-efficient, voltage-controlled light valves, such as watch andcalculator displays, and flat-panel displays as are found in portablecomputers and compact televisions.

Liquid crystal displays have a number of unique characteristics,including low voltage and low power of operation, which make them themost promising of the non-emissive electrooptical display candidatescurrently available. However, slow response and insufficientnonlinearity can impose limitations for many potential applications. Therequirement for speed may become especially important in proportion tothe number of elements which have to be addressed in a device. Thislimits the potential use of some types of liquid crystals.

The modes of liquid crystal displays that are most extensively employedat the present are twisted nematic (TN), supertwisted birefringenceeffect (SBE), and dynamic scattering (DS), all employing nematic orchiral nematic (cholesteric) liquid crystals. These devices are basedupon the dielectric alignment effects (Freedericksz effect) of thenematic and/or chiral nematic liquid crystal or mixtures of nematic orchiral nematic liquid crystals upon application of an electric field.The average molecular long axis of the liquid crystal material takes upa preferred orientation in the applied electric field, the orientationof which is dependent on the sign of the dielectric anisotropy of thematerial or mixture, and this orientation relaxes upon removal of theapplied electric field. This reorientation and relaxation is slow, onthe order of a few milliseconds.

Although nematic and chiral nematic liquid crystals are the mostextensively employed, there are liquid crystal devices that employhigher ordered smectic liquid crystals.

Devices employing materials with a smectic A mesophase are useful indevice applications as described in Crossland, et al. U.S. Pat. Nos.4,411,494; 4,419,664; and 4,528,562; and F. J. Kahn (Appl. Phys. Lett.,vol. 22, p. 111 (1973). These devices are based on the dielectricreorientation of the liquid crystals and response times are on the orderof milliseconds.

Mixtures which exhibit a chiral smectic A mesophase are useful in adevice as described by Lagerwall, et al. 1st International Symposium OnFerroelectric Liquid Crystals, Bordeaux-Arcachon, France, 1987. Thesemixtures exhibit an electrooptic effect which is termed a soft-modeferroelectric effect and sub-microsecond switching can be achieved.

Devices employing materials with a smectic C mesophase are useful indevice applications as described by Pelzl, et al. (Kristall Technik.,vol. 14, p. 817 (1979); Mol. Cryst. Liq. Cryst., vol. 53, p. 167 (1979);Liquid Crystals, vol. 2, p. 21 (1987); and Liquid Crystals, vol. 2, p.131 (1987)). These devices are based on the dielectric reorientation ofthe liquid crystals and the response times are slow.

A recent advance in the liquid crystal art has been the utilization oftilted chiral smectic liquid crystals, which are also termedferroelectric liquid crystals, in devices which give microsecondswitching and bistable operation not possible in any of the deviceapplications described above. Ferroelectric liquid crystals werediscovered by R. B. Meyer, et al. (J. Physique, vol. 36, pp. 1-69,1975). A high speed optical switching phenomenon was discovered for theferroelectric liquid crystals by N. A. Clark, et al. (Appl. Phys. Lett.,vol. 36, p. 899 (1980) and U.S. Pat. No. 4,367,924).

Fluorine-containing ferroelectric liquid crystal materials have recentlybeen developed. U.S. Pat. No. 4,886,619 (Janulis) disclosesfluorine-containing chiral smectic liquid crystal compounds whichcomprise a fluorocarbon terminal portion and a chiral hydrocarbonterminal portion with the terminal portions being connected by a centralcore. U.S. Pat. No. 5,082,587 (Janulis) discloses achiralfluorine-containing liquid crystal compounds which comprise afluorocarbon terminal portion and a hydrocarbon or another fluorocarbonterminal portion, the terminal portions being connected by a centralcore.

International Publication No. WO 91/00897 (Merck) discloses chiral orachiral ring compounds which may be used as components of chiral,tilted, smectic liquid-crystalline phases with ferroelectric properties.The compounds have the formula

    R.sup.1 --A.sup.1 --A.sup.2 --Q--(CH.sub.2).sub.m --(CF.sub.2).sub.n --X

where R¹ is an alkyl or perfluoroalkyl group with 1 to 12 carbon atoms,in which one or two non-adjacent CH₂ or CF₂ groups may be replaced byO-atoms, and/or --CO--, --COO--, --CH═CH--, --CH--halogen--, --CHCN--,--OCOCH--halogen--, or --COO--CHCN-- groups or where R¹ is X--(CF₂)_(n)--(CH₂)_(m) --Q-- and X is H or F; A¹ and A² are mutually independentlyunsubstituted 1,4-phenylene groups or 1,4-phenylene groups substitutedby one or two F-atoms, whereby one or two CH--groups may may besubstituted by N; Q is --O--, --COO--, --OCO-- or a single bond; m is 1to 10; and n is 2 to 8, with the proviso that m is 3 to 10 if Q is--COO-- or --OCO--.

The high speed switching of the ferroelectric liquid crystals can beutilized in many applications: light valves, displays, printer heads,and the like. In addition to the submicrosecond switching speeds, someferroelectric device geometries exhibit bistable, threshold sensitiveswitching, making them candidates for matrix addressed devicescontaining a large number of elements for passive displays of graphicand pictorial information, as well as optical processing applications.

SUMMARY OF THE INVENTION

The present invention provides fluorine-containing liquid crystalcompounds comprising an aliphatic fluorocarbon terminal portion havingat least one catenary ether oxygen and an aliphatic hydrocarbon terminalportion, the terminal portions being connected by a central core, thecompounds having smectic mesophases or having latent smectic mesophases.Compounds having latent smectic mesophases are those which by themselvesdo not exhibit a smectic mesophase, but when the compounds are inadmixture with said compounds having smectic mesophases or other saidcompounds having said latent smectic mesophases develop smecticmesophases, under appropriate conditions. The fluorocarbon terminalportion can be represented by the formula --D(C_(x) F_(2x) O)_(z) C_(y)F_(2y+1) where x is 1 to 10, y is 1 to 10, z is 1 to 4 and D is acovalent bond, ##STR1## where r and r' are independently 1 to 20 and pis 0 to 4.

In general, the compounds of this invention have a central corecomprised of at least two rings independently selected from aromatic,heteroaromatic, cycloaliphatic, or substituted aromatic, heteroaromatic,or cycloaliphatic rings, connected one with another by a covalent bondor by groups selected from --COO--, --COS--, --HC═N--, --COSe--. Ringsmay be fused or non-fused. Heteroatoms within the heteroaromatic ringcomprise at least one atom selected from N, O, or S. Non-adjacentmethylene groups in cycloaliphatic rings may be substituted by O or Satoms.

The fluorine-containing liquid crystal compounds having fluorocarbonterminal portions of the present invention are not optically active butare useful, for example, when used in mixtures with optically activeliquid crystal materials. These compounds have a number of desirableproperties when used in admixture with fluorinated ferroelectric liquidcrystal with perfluoroaliphatic terminal portions such as thosedisclosed, for example, in U.S. Pat. No. 4,886,619 and U.S. Pat. No.5,082,587. The compounds having perfluoroether terminal portions of thepresent invention possess lower temperature smectic A and C phases thancompounds having perfluoroaliphatic terminal portions without an etherlinkage having substantially the same number of carbon atoms in theterminal portion.

The inclusion of the liquid crystal compounds of the invention inmixtures with fluorinated ferroelectric liquid crystals withperfluoroaliphatic terminal portions results in compositions with lowerviscosity and faster switching time than with mixtures without theliquid crystal compounds of the invention.

The presence of the compounds having perfluoroether terminal portionsincreases the temperature range of the smectic C phase of the admixture.A device containing such admixture will function only in the desiredsmectic C phase of the mixture. The compounds of the present inventionhaving perfluoroether terminal portions have lower transitions fromsmectic C to higher order and, thus, act to prevent admixtures fromgoing from smectic C to higher order until the admixture temperature islower than that at which the compounds having perfluoroaliphaticterminal portions would normally change to higher order.

The fluorine-containing liquid crystal compounds having perfluoroetherterminal portions also have good chemical stability towards water, weakacids and weak bases, do not undergo degradation during normal use in aliquid crystal display device, and are photochemically stable, that is,they do not easily undergo photochemical reactions. These compounds, dueto the novel fluorocarbon terminal portion, have greatly enhancedsmectogenic properties, lower birefringences, and lower viscosities thantheir non-fluorine-containing analogues.

These fluorinated liquid crystal compounds having perfluoroetherterminal portions and mixtures which contain them are useful in avariety of electrooptical displays. In particular, these fluorinatedmaterials exhibit smectic mesophases, especially smectic A and C, andare useful in the formulation of smectic A (SmA), smectic C (SmC),chiral smectic A (SmA*), and chiral smectic C (SmC*) mixtures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows comparative Smectic A and Smectic C phases for prior artliquid crystal materials and liquid crystal materials of the inventionas determined by DSC.

FIG. 2 shows comparative Smectic A and Smectic C phases for prior artliquid crystal materials and liquid crystal materials of the inventionas determined by optical microscopy.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to fluorine-containing liquid crystalcompounds having perfluoroether terminal portions and mixtures derivedtherefrom which find use in smectic liquid crystal display applicationsand the like. The liquid crystals of the present invention can berepresented by the general formula I: ##STR2## where M, N, and P areeach independently ##STR3## a, b, and c are each independently zero oran integer of from 1 to 3 with the proviso that the sum of a+b+c be atleast 2;

each A and B are non-directionally and independently a covalent bond,##STR4## each X, Y, and Z are independently --H, --Cl, --F, --Br, --I,--OH, --OCH₃, --CH₃, --CF₃, --OCF₃ --CN, or --NO₂ ;

each 1, m, and n are independently zero or an integer of 1 to 4,

D is a covalent bond, ##STR5## where r and r' are independently 1 to 20and where r and and r' are independently 1 to 20, and p is 0 to 4;##STR6## where R' is --Cl, --F, --CF₃, --NO₂, --CN, --H, ##STR7## and qand q' are independently 1 to 20, and R can be straight chain orbranched; and

R_(f) is --(C_(x) F_(2x) O)_(z) C_(y) F_(2y+1) where x is independently1 to 10 for each C_(x) F_(2x) O, y is 1 to 10 and z is 1 to 6.

A preferred class of compounds of the invention have a pyrimidine coreand can be represented by the formula ##STR8## where d is 5 to 10, x isindependently 1 to 3 for each C_(x) F_(2x) O, y is 1 to 4 and z is 1 to3.

Compounds of the present invention have birefringences typically in therange of 0.05-0.18 depending on the ring systems present and the numberof rings, suppressed nematic mesophases, i.e., exhibit no or very smallnematic mesophase temperature ranges and enhanced smectic mesophases.Mixtures of the compounds of the invention with other liquid crystalmaterials can be formulated to provide desired transition temperaturesand broad mesophase temperature ranges. Such mixtures preferably containfluorine-containing chiral smectic liquid crystals as disclosed in U.S.Pat. No. 4,886,619 (Janulis) and/or achiral fluorine-containing liquidcrystals as disclosed in U.S. Pat. No. 5,082,587, each of which isincorporated herein by reference.

The individual compounds of this invention which exhibit smectic Abehavior can be used in admixture with other materials in smectic Adevice applications (see Crossland, et al. U.S. Pat. Nos. 4,411,494,4,419,664, and 4,528,562, which are incorporated herein by reference,and F. J. Kahn (Appl. Phys. Lett., vol. 22, p. 111 (1973).

The individual compounds of this invention which exhibit smectic Cbehavior can be used in admixture with other materials in the smectic CFreedericksz device application described by Pelzl et al., (see KristallTechnik., vol. 14, p. 817 (1979); Mol. Cryst. Liq. Cryst., vol. 53, p.167 (1979); Liquid Crystals, vol. 2, p. 21 (1987); and Liquid Crystals,vol. 2, p. 131 (1987)). As pointed out in the studies of Pelzl, et al.the decay time in the smectic C phase is shorter than in the nematicphase of the same material and in some cases the rise times are shorter,making this type of device application preferential to utilizingnematics in the classical Freedericksz device mode for someapplications. The rise and decay times for the materials examined byPelzl, et al. were on the order of 2-100 milliseconds for a 50% changein the measured light intensity. For materials of the present invention,rise and decay times of less than 1 millisecond have been observed foran 80% change in the light intensity. Rise and decay times of a fewmilliseconds for an 80% change in the light intensity have been observedin room temperature mixtures. Devices utilizing materials of the presentinvention make practical the use of smectic C materials in place ofnematic materials in Freedericksz type devices and significantly shorterrise and decay times are attainable.

The compounds of this invention do not show chiral smectic(ferroelectric) liquid crystal behavior by themselves since they areachiral. However, a preferred embodiment of this invention comprisesmixtures which contain materials of this invention with at least onechiral (optically active) component. The broad smectic C mesophaseranges and lower temperature smectic C mesophases of many of thematerials of this invention make them useful and desirable as componentsin the formulation of broad smectic C eutectics, which becomeferroelectric, or chiral smectic C, upon addition of a chiral additive.

Other advantages of using the materials of this invention in theformulation of chiral smectic mixtures are the low birefringence andviscosity which can be obtained. The lower viscosity of these materialsresults in reduced response times for the ferroelectric switching for agiven bulk polarization value. The lower birefringence of thesematerials allows the fabrication of devices with larger device spacings.Light transmission through a surface-stabilized ferroelectric device (asdescribed in U.S. Pat. No. 4,367,924, which is incorporated by referenceherein) with two polarizers is represented by the following equation:

    I=I.sub.o (sin.sup.2 (4Θ)) (sin.sup.2 (πΔnd/λ))

where

I_(o) =transmission through parallel polarizers

Θ=material tilt angle

Δn=liquid crystal birefringence

d=device spacing

λ=wavelength of light used

To maximize the transmission, both sin² (4Θ) and sin² (πΔnd/λ) must beat maximum. This occurs when each term equals one. The first term is amaximum when the tilt angle equals 22.5°. This is a function of theliquid crystal and is constant for a given material at a giventemperature. The second term is maximum when Δnd =λ/2.

This demonstrates the criticality of the low birefringence of thematerials of this invention. Low birefringence allows a larger devicethickness, d for a given wavelength of light. Thus, a larger devicespacing is possible while still maximizing transmission, allowing easierdevice construction.

The fluorine-containing liquid crystal compounds having perfluoroetherterminal portions of the invention can be prepared by a processcomprising the steps of (1) mixing at least one compound represented bythe formula ##STR9## with at least one compound represented by theformula ##STR10## or (2) mixing at least one compound represented by theformula ##STR11## with at least one compound represented by the formula##STR12## where M, N, and P are each independently ##STR13## a, b, and care each independently zero or an integer of from 1 to 3 with theproviso that the sum of a+b+c be at least 2;

each A and B are nondirectionally and independently a covalent bond,##STR14## each A', A", B', and B" are independently --OH, --COOH,--CH(CH₂ OH)₂, --SH, --SeH, --TeH, --NH₂, --COCl, --CHO, --OSO₂ CF₃ or--CH₂ COOH with the proviso that A' can enter into an addition orcondensation reaction with A" and B' can enter into an addition orcondensation reaction with B"; each X, Y, and Z are independently --H,--Cl, --F, --OCH₃, --OH, --CH₃, --NO₂, --Br, --I, or --CN;

each l, m, and n are independently zero or an integer of 1 to 4;

R is --OC_(q) H_(2q) --OC_(q') H_(2q'+1), ##STR15## independently 1 to20, and p is 0 to 4; R_(f) is --(C_(x) F_(2x) O)_(z) C_(y) F_(2y+1)where x is independently 1 to 10 for each C_(x) F_(2x) O group, y is 1to 10 and z is 1 to 6; and allowing said A' and A" or B' and B" to reactin the presence of suitable coupling agents, i.e., a reagent whicheffects coupling.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

In the following examples, all temperatures are in degrees Centigradeand all parts and percentages are by weight unless indicated otherwise.Commercially available materials were chemically transformed by reactionpathways well-known to those skilled in the art and detailed in theexamples. Chemical transformations were comprised of acylation,esterification, etherification, alkylation, and combinations thereofusing fluorine-containing and non-fluorine-containing reactants toprovide the precursor compounds, which, in turn were caused to reacttogether to yield the achiral fluorine-containing liquid crystalcompounds of this invention.

Compounds prepared in the various examples of this invention werecharacterized by their melting or boiling point and structures wereconfirmed by using at least one of the methods of analysis:chromatography, ¹³ C--, ¹ H-- and ¹⁹ F-NMR, IR and MS spectroscopies.

Examples 1-13 describe procedures for preparing intermediate compoundsuseful in preparing the liquid crystal compounds of this invention.Examples 14-33 describe preparation of the liquid crystal compounds ofthis invention.

The 5-alkyl-2-(4-hydroxyphenyl)pyrimidines used in the examples wereprepared using the method described by Zaschke, H. and Stolle, R. in"Synthese niedrigschmelzender Kristallin-Flussiger hetercyclen;5-n-Alkyl-2-[4-n-alkanoyloxy-phenyl]pyrimidine", Z. Chem., (15), pp.441-443 (1975).

EXAMPLE 1

Cell drainings derived from the electrochemical fluorination of methyl3-methoxypropanoate (45 g, 55% perfluoro-3-methoxypropionyl fluoride)were chilled to -78° C. in a dry ice acetone bath in a flask fitted witha -78° C. condenser, overhead stirrer, thermometer, and addition funnel.The exit line to the condenser was fitted with a drying tower. Over aperiod of 5 minutes, methanol (6 g) was added to the rapidly stirredsolution. The flask was warmed to 0° C. and stirring was continued forone hour. At that time, the reaction mixture was allowed to warm to roomtemperature and then was stirred for an additional two hours. Water (100mL) was added and the reaction mixture was allowed to phase split. Thelower fluorochemical phase (40 g) was washed again with water (50 mL) togive 33 g of crude product. The crude product was added to a flaskfitted with a 10.2 cm distillation column filled with steel helices anda distillation splitter. Polyphosphoric acid (9 g) was added to thedistillation pot and the fluorochemical product was distilled. Twoproduct cuts were obtained: boiling at 80°-84° C. (5.2 g, 64% methylperfluoro-3-methoxypropanoate), boiling at 84°-87° C. (6.5 g, 78% methylperfluoro-3-methoxypropanoate). The GC-mass spectrum of the secondproduct cut confirmed the identity of the major peak as CF₃ OCF₂ CF₂ CO₂CH₃, methyl perfluoro-3-methoxypropanoate.

Sodium borohydride (5.0 g) was added to a flask fitted with a condenser,overhead stirrer, thermometer, and addition funnel. The sodiumborohydride was slurried with 40 g of tetraglyme. With good stirring,the methyl perfluoro-3-methoxypropanoate (30.3 g) was added over a 30minute period. The reaction mixture was heated at 90° C. for two hours.The reaction mixture was cooled to room temperature and poured intowater (40 g). After the addition of the crude reaction product wascomplete, concentrated sulfuric acid (6.0 g) was added to thewater/product mixture. The water/product mixture was returned to theflask and the product isolated by azeotropic distillation with water. ABarret trap was placed between the flask and the condenser. The crudereaction mixture was heated so that the product/water would distill intothe trap. In the trap, the azeotrope split into two layers and the upperwater layer was recycled to the flask. A total of 27.2 g offluorochemical product was isolated from the trap. Karl Fischer wateranalysis showed the product to be 5.46 weight percent water. The productwas added to polyphosphoric acid (23 g) and heated at 60° C. for onehour. The resultant product was one-plate distilled from thepolyphosporic acid. The desired product (15.7 g) distilled at 96°-100°C. Analysis showed this material to be 0.1 weight percent water. F-NMRshowed this material to contain the following: 91.1 mole % of thedesired product, CF₃ OCF₂ CF₂ CH₂ OH,1,1-dihydroheptafluoro-3-methoxypropanol, 6.0 mole % CF₃ CF₂ CH₂ OH, and1.2 mole % CF₃ CF₂ CF₂ CH₂ OH.

1,1-Dihydroheptafluoro-3-methoxypropanol (13.77 g, 0.0637 moles) andtriethylamine (9.75 mL, 0.0701 moles) were dissolved in methylenechloride (25 mL) in a 100 mL flask fitted with a magnetic stir bar, lowtemperature thermometer, septum, and a nitrogen bubbler. The contents ofthe flask were then cooled to -20° C. and triflic anhydride (10.7 mL,0.0637 moles) were added slowly via syringe to maintain the temperaturebelow -15° C. After the addition was complete, the reaction was allowedto warm to room temperature. The solution was transferred to aseparatory funnel and washed twice with 30 mL 0.5 N HCl and once with 30mL water. The resulting solution was finally distilled and 8.75 mL ofmaterial boiling at 118°-120° C. were collected. GC showed 69 area % ofthe main component, 1,1-dihydroheptafluoro-3-methoxypropyl triflate.

EXAMPLE 2

Cell drainings derived from the electrochemical fluorination ofethoxyethyl acetate (235 g, 17% perfluoro-2-ethoxyacetyl fluoride) werechilled to -78° C. in a dry ice acetone bath in a flask fitted with a-78° C. condenser, overhead stirrer, thermometer, and addition funnel.The exit line to the condenser was fitted with a drying tower. Over aperiod of.5 minutes, methanol (12 g) was added to the rapidly stirredsolution. The flask was warmed to 0° C. and stirring was continued forone hour. At that time, the reaction mixture was allowed to warm to roomtemperature and then was stirred overnight. Then, concentrated sulfuricacid (6 mL) was added and the reaction mixture phase-split. The lowerfluorochemical phase was split away from the upper sulfuricacid/methanol/HF phase. A total of 101 g of crude product was isolated.GC showed this material to be 16 weight percent CF₃ CO₂ CH₃ and 26weight percent CF₃ CF₂ OCF₂ CO₂ CH₃ ; gc/mass spectrum confirmed theidentity of these peaks. The crude product was added to a flask fittedwith a 10.2 cm distillation column filled with steel helices and adistillation splitter. Four product cuts were obtained: boiling at65°-70° C. (5.8 g, 27% methyl perfluoro-2-ethoxyacetate), boiling at70°-75° C. (6.4 g, 34% methyl perfluoro-2-ethoxyacetate), boiling at75°-80° C. (16.8 g, 36% methyl perfluoro-2-ethoxyacetate), boiling at80°-82° C. (16.1 g, 44% methyl perfluoro-2-ethoxyacetate). The fourproduct cuts were combined. The GC-mass spectrum of the blended productconfirmed the identity of the major product peak as CF₃ CF₂ OCF₂ CO₂CH₃, methyl perfluoro-2-ethoxyacetate.

Sodium borohydride (5.6 g) was added to a flask fitted with a condenser,overhead stirrer, thermometer, and addition funnel. The sodiumborohydride was slurried with tetraglyme (45 g). With good stirring, themethyl perfluoro-2-ethoxyacetate (45.1 g, 37% methylperfluoro-2-ethoxyacetate) was added over a 30 minute period. Thereaction mixture was heated at 90° C. for two hours. The reactionmixture was cooled to room temperature and poured into water (80 g).After the addition of the crude reaction product was complete,concentrated sulfuric acid (7.2 g) was added to the water/productmixture. The water/product mixture was returned to the flask and theproduct isolated by azeotropic distillation with water. A Barret trapwas placed between the flask and the condenser. The crude reactionmixture was heated to distill the product/water into the trap. In thetrap, the azeotrope split into two layers and the upper water layer wasrecycled to the flask. A total of 20.5 g of fluorochemical product wasisolated from the trap. Gas chromatography (GC) showed the product to be66% desired product, CF₃ CF₂ OCF₂ CH₂ OH,1,1-dihydroheptafluoro-2-ethoxyethanol. The GC/mass spectrum showed thismaterial to consist of 73.8% CF₃ CF₂ OCF₂ CH₂ OH, 5.8% CF₃ OCF₂ CH₂ OHand 2.3% CF₃ CF₂ OCF₂ CF₂ CH₂ OH.

1,1-Dihydro-heptafluoro-2-ethoxyethanol mixture, as described above(19.6 g, 82% fluorochemical alcohols), was dissolved in methylenechloride (30 mL) and dried with silica gel (0.9 g, 100-200 mesh, 983grade) and filtered. The methylene chloride solution was placed in aflask fitted with a magnetic stirrer, thermometer, and addition funnel.Triethylamine (12.4 g) was added to the flask, and the internaltemperature rose to 40° C. The flask was cooled to 5° C. in an ice bath,and then triflic anhydride (34.1 g) was added slowly so that thetemperature did not exceed 10° C. The reaction mixture stirred overnightwith warming to room temperature. Water (50 mL) and methylene chloride(20 mL) were added and the mixture allowed to phase split. The lowerproduct phase was then washed with 3% sulfuric acid (50 mL) and water(20 mL). The methylene chloride was then stripped off at atmosphericpressure. The product cut distilled at a head temperature of 107°- 115°C. A total of 10.4 g of product was obtained. The GC/mass spectrumshowed this material to consist of 75.7 area % CF₃ CF₂ OCF₂ CH₂ OSO₂CF₃. F-NMR showed this material to consist of the following weight %:87.0% CF₃ CF₂ OCF₂ CH₂ OSO₂ CF₃, 4.6% CF₃ CF₂ CF₂ CF₂ OCF₂ CH₂ OSO₂ CF₃,0.3% CF₃ CF₂ CF₂ OCF₂ CH₂ OSO₂ CF₃.

EXAMPLE 3

Sodium borohydride (8.3 g) was added to a flask fitted with a condenser,overhead stirrer, thermometer, and addition funnel. The sodiumborohydride was slurried with tetraglyme (100 g). With good stirring,methyl perfluoro-2-(butoxyethoxy)acetate (100 g, prepared byfluorination and methanolysis of butoxyethoxyethyl acetate) was addedover a 30 minute period. The reaction mixture was heated at 90° C. fortwo hours and then cooled to 40° C. Methanol (18 g) was added slowly.The reaction mixture was heated at 50° C. for 30 minutes, then water(160 g) was rapidly added. After the addition of the water was complete,concentrated sulfuric acid (11 g) was added to the water/productmixture. The crude product was washed with water (160 g) to yield 95 gcrude product. The crude product was distilled at 160 Pa (1.2 mm Hg) ata head temperature of 51°-60° C. to give 77.8 g of the desired product,1,1-dihydroperfluoro-2-(butoxyethoxy) ethanol.

1,1-Dihydro-perfluoro-2-(butoxyethoxy)ethanol (10 g) was dissolved inmethylene chloride (30 mL) and placed in a flask fitted with a magneticstirrer, thermometer, and addition funnel. Triflic anhydride (8.1 g) wasadded to the flask. The flask was cooled to 5° C. in an ice bath, andthen triethylamine (2.9 g) was added slowly so that the temperature didnot exceed 10° C. The reaction mixture was stirred overnight withwarming to room temperature. Water (20 mL) and methylene chloride (10mL) were added and the mixture was allowed to phase split. The lowerproduct phase was then washed with 3% sulfuric acid (20 mL) and water(10 mL). The methylene chloride was then stripped off atmospherically.The product cut distilled at a head temperature of 92--95° C. at 60 kPa(45 mm Hg). A total of 9.4 g of product was obtained. GC/mass spectrumshowed this material to consist of 88 area % of the desired product, CF₃(CF₂)₃ OCF₂ CF₂ OCF₂ CH₂ OSO₂ CF₃, 1,1-dihydroperfluoro-2-(butoxyethoxy)ethyl triflate, and 10 area % CF₃ SO₂ N(C₂ H₅)₂.

EXAMPLE 4

4-Cyano-4'-hydroxybiphenyl was converted to the corresponding amidinehydrochloride via the method of M. W. Partridge and W. F. Short (J.Chem. Soc.(1947), p. 390). The amidine hydrochloride (10 g, 0.0402moles) and 2-octyl-3-dimethylaminoacrolein (8.5 g, 0.0402 moles,prepared as described by Z. Arnold, and F. Sorm, Coll. Czech. Chem.Commun., 23(1958) p. 452) were then treated with 25% sodium methoxide inmethanol (37 mL, 0.1608 moles) in 150 mL of absolute ethanol. Theresulting mixture was heated to reflux and refluxed overnight. Aftercooling to room temperature, the solvent was removed under reducedpressure. Water (100 mL), ether (100 mL) and acetic acid (10 mL) werethen added to the flask and the mixture was stirred until the solidsdissolved. The resulting layers were separated. The aqueous layer wasextracted twice with ether (50 mL). The combined ether layers werewashed three times with water (50 mL), and dried with anhydrousmagnesium sulfate. Finally, the solvent was removed under reducedpressure, and the resulting solid was recrystallized from hotacetonitrile to yield 5.38 g (37%) of the desired product,5-octyl-2-(4'-hydroxybiphenyl)pyrimidine.

EXAMPLE 5

4-Benzyloxyphenol (10 g, 0.0499 moles) was slowly added to 60% sodiumhydride in mineral oil (2.8 g) suspended in 100 mL of drydimethoxyethane. After stirring the resulting solution for 30 minutes atroom temperature, it was cooled with a dry ice/acetone bath.1,1-dihydroheptafluoro-2-ethoxyethyl triflate (18 g, Example 2) was thenadded slowly. When the addition was complete, the ice bath was removed,and the mixture was stirred at room temperature overnight. The solventwas then removed under reduced pressure and water (200 mL), and ether(150 mL) were added. When the solids had dissolved, the layers wereseparated and the aqueous layer was extracted twice with ether (150 mL).The combined ether layers were washed once with 1N sodium hydroxide (125mL) and twice with water (150 mL), dried with anhydrous magnesiumsulfate, and stripped to dryness on a rotary evaporator. The resultingsolid (13 g) was dissolved in ethanol and hydrogenated at 0.4 MPa (60psi) in the presence of catalytic 10% palladium on carbon for 18 hours.When the hydrogenation was complete the catalyst was removed byfiltration, and the solvent was removed on a rotary evaporator. Theresulting solid (6.5 g) was recrystallized from petroleum ether to yield4 g of 4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol.

EXAMPLE 6

In this example, a compound was prepared in the same manner as thatdescribed in Example 5, except that1,1-dihydroperfluoro-2-(butoxyethoxy)ethyl triflate (28 g, 0.049 moles)was substituted for the 1,1-dihydroheptafluoro-2-ethoxyethyl triflate,to provide 7.6 g of4-(1,1-dihydroperfluoro-2-(butoxyethoxy)ethoxy)phenol.

EXAMPLE 7

4'-Benzyloxy-4-hydroxybiphenyl (1.5 g, 0.0054 moles) was slowly added to60% sodium hydride in mineral oil (0.3 g) suspended in drydimethoxyethane (15 mL). After stirring the resulting solution for 20minutes at room temperature, it was cooled with an ice bath.1,1-Dihydroheptafluoro-2-ethoxyethyl triflate (1.9 g, 0.0055 moles) wasthen added slowly. When the addition was complete, the ice bath wasremoved, and the mixture stirred at room temperature overnight. Thesolvent was then removed under reduced pressure, and water (25 mL) andethyl ether (25 mL) were added. When the solids had dissolved, thelayers were separated and the aqueous layer was extracted three timeswith ether (15 mL). The combined ether layers were washed three timeswith water (20 mL), dried with anhydrous magnesium sulfate, and solventremoved on a rotary evaporator. The resulting solid was dissolved intetrahydrofuran and hydrogenated at 0.4 MPa (60 psi) in the presence ofcatalytic 10% palladium on carbon for 18 hours. When the hydrogenationwas complete the catalyst was removed by filtration, and the solvent wasremoved on a rotary evaporator. The resulting solid was recrystallizedfrom hexane to yield 1.2 g of4'-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-4hydroxybiphenyl.

EXAMPLE 8

In this example, a compound was prepared in the same manner as thatdescribed in Example 7, utilizing 0.3 g of 60% sodium hydride in mineraloil, 15 mL of dimethoxyethane, 1.0 g (0.0036 moles) of4'-benzyloxy-4-hydroxybiphenyl, except that1,1-dihydroperfluoro-2-(butoxyethoxy)ethyl triflate (2.3 g, 0.0040moles) was substituted for the 1,1-dihydroheptafluoro-2-ethoxyethyltriflate, to provide 1.0 g of4'-(1,1-dihydroperfluoro-2-(butoxyethoxy)ethoxy)-4-hydroxybiphenyl.

EXAMPLE 9

6-Benzyloxy-2-napthol (2.5 g, 0.010 moles) was slowly added to 60%sodium hydride in mineral oil (0.7 g) suspended in dry dimethoxyethane(25 mL). After stirring the resulting solution for 20 minutes at roomtemperature, it was cooled with an ice bath.1,1-Dihydroheptafluoro-2-ethoxyethyl triflate (3.8 g, 0.011 moles) wasthen added slowly. When the addition was complete, the ice bath wasremoved and the mixture was stirred at room temperature overnight. Thesolvent was then removed under reduced pressure and water (30 mL) andether (30 mL) were added. When the solids had dissolved, the layers wereseparated and the aqueous layer was extracted twice with ether (25 mL).The combined ether layers were washed three times with water (20 mL),dried with anhydrous magnesium sulfate and stripped to dryness on arotary evaporator. The resulting solid was dissolved in tetrahydrofuranand hydrogenated at 0.4 MPa (60 psi) in the presence of catalytic 10%palladium on carbon for 18 hours. When the hydrogenation was completethe catalyst was removed by filtration, and the solvent was removed on arotary evaporator. The resulting solid was recrystallized from hexane toyield 1.28 g of6-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-2-hydroxynapthalene.

EXAMPLE 10

In this example, a compound was prepared in the same manner as thatdescribed in Example 9, except that1,1-dihydroperfluoro-2-(butoxyethoxy)ethyl triflate (6.2 g, 0.010 moles)was substituted for the 1,1-dihydroheptafluoro-2-ethoxyethyl triflate,to provide 2.5 g of6-(1,1-dihydroperfluoro-2-(butoxyethoxy)ethoxy)-2-hydroxynapthalene.

EXAMPLE 11

Sodium hydride (0.39 g of 80% suspension in mineral oil) was added todimethyl formamide (5 mL) in a three-necked flask under an inertatmosphere. Methyl hydroxybenzoate (1.96 g, 0.129 moles) was dissolvedin a mixture of toluene (10 mL) and dimethyl formamide (5 mL). Themethyl hydroxybenzoate solution was added to the sodium hydride over aperiod of 15 minutes. The reaction was allowed to stir at roomtemperature for one hour. 1,1-Dihydroheptafluoro-2-ethoxyethyl triflate(4.5 g, 0.129 moles) was then added and the flask was heated to 116° C.for one hour. The reaction mixture was cooled to room temperature andpoured into water (25 mL). The upper product phase was split off andrewashed with additional water (25 mL). The crude product solution wasthen stripped at 26.7 Pa (0.2 mm Hg) until the pot temperature reached12O° C. The product was then distilled at 4 Pa (0.03 mm Hg). The product(3.7 g) distilled at 100°-105° C. head temperature and consisted of awhite low melting solid. GC-mass spectrum showed the material to consistof 89% of the product, methyl4-(2,2-difluoro-2-pentafluoroethoxyethoxy)benzoate, with a molecularweight of 350, 5% of a material with a molecular weight of 430, and 6%of the starting methyl hydroxybenzoate. The infrared spectrum wasconsistent with the desired structure.

Subsequently, the methyl4-(2,2-difluoro-2-pentafluoroethoxyethoxy)benzoate (3.3 g) was heated atreflux with 10% KOH (20 mL) for 2 hours. The hydrolysis reaction wasthen cooled to room temperature, and acidified with 98% sulfuric acid(1.75 g). The fluorinated benzoic acid precipitated, was isolated byfiltration and washed twice with water (10 mL). The crude acid was thenstirred with ethanol (50 mL) and filtered. The cake was washed with anadditional 25 mL of ethanol. The material was dried in a vacuum oven atroom temperature and 26.7 Pa (0.2 mm Hg). The desired4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)benzoic acid (2.7 g) wasisolated.

EXAMPLE 12

Sodium (1.15 g, 50 mmoles) was reacted with anhydrous ethanol (200 mL)under a nitrogen atmosphere. 2,3-dicyanohydroquinone (8.01 g, 50 mmoles)in anhydrous ethanol (50 mL) was added dropwise to the ethoxidesolution. Upon completion of the addition, potassium iodide (0.5 g) in 5mL water was added. This solution was brought to reflux and octylbromide (9.66 g, 50 mmoles) was added dropwise. The reaction was thenrefluxed under nitrogen atmosphere for one day. The mixture wasacidified with 0.5N aqueous HCl and the solvents were removed underreduced pressure. The crude reaction mixture was flash chromatographedusing silica gel and methylene chloride as eluent. The appropriatefractions containing the desired product, 2,3-dicyano-4-octyloxyphenol,were combined and the solvent removed under reduced pressure on a rotaryevaporator. The crude product was recrystallized from ethanol/water togive 4.5 g 2,3-dicyano-4-octyloxyphenol.

EXAMPLE 13

2,3-Difluoro-4-octyloxyphenol was prepared as described in Reiffenrath,V. et al., "New Liquid Crystalline Compounds With Negative DielectricAnisotrophy" Liquid Crystals, 5, (1989), pp. 159-170.

EXAMPLE 14

A 100 mL 3-neck flask fitted with a magnetic stir bar, septum, stopper,and water cooled condenser connected to a nitrogen bubbler was chargedwith dry sodium hydride (0.8 g, 0.0345 moles), toluene (20 mL), anddimethyl formamide (20 mL). With vigorous stirring,5-hexyl-2-(4-hydroxyphenyl)pyrimidine (5.9 g, 0.023 moles) was addedslowly to control the hydrogen evolution. The resulting mixture wasstirred at room temperature for 30 minutes. Then,1,1-dihydroheptafluoro-3-methoxypropyl triflate (8 g, 0.023 moles,prepared in Example 1) was added and the solution was heated to reflux.After 1 hour, the reaction mixture was allowed to cool to roomtemperature. The contents of the flask were poured into a separatoryfunnel containing water (50 mL). The resulting layers were separated andthe aqueous layer was extracted twice with toluene (20 mL). The combinedorganic layers were then washed three times with water, dried withanhydrous sodium sulfate, and filtered. After solvent removal on arotary evaporator, a brown oil resulted. This oil was chromatographed onsilica gel (125 g), eluting with chloroform. Care was taken to separatethe product from a yellow impurity which eluted off the column justbefore and overlapping with the desired product. A pale yellow semisolid(liquid crystalline at room temperature) resulted. The yield of thisdesired product,5-hexyl-2-(4-(1,1-dihydroheptafluoro-3-methoxypropoxy)phenyl)pyrimidine,Compound 1, Table 1, was 2.8 g.

EXAMPLE 15

A 100 mL 3-neck flask fitted with a magnetic stir bar, septum, stopper,and water cooled condenser connected to a nitrogen bubbler was chargedwith 60% sodium hydride/mineral oil (1.6 g, 0.04 moles), toluene (25mL), and dimethyl formamide (25 mL). With vigorous stirring,5-octyl-2-(4-hydroxyphenyl)pyrimidine (7.6 g, 0.0267 moles) was addedslowly to control the hydrogen evolution. The resulting mixture wasstirred at room temperature for 30 minutes. Then,1,1-dihydroheptafluoro-2-ethoxyethyl triflate (9.3 g, 0.0267 moles,prepared as in Example 2) was added and the solution was heated toreflux. After 1 hour, the reaction mixture was cooled to roomtemperature. The contents of the flask were poured into a separatoryfunnel containing water (50 mL). The resulting layers were separated,and the aqueous layer was extracted twice with toluene (20 mL). Thecombined organic layers were then washed three times with water, treatedwith silica gel (5 g) for one hour and filtered. After solvent removalon a rotary evaporator, a light brown oil resulted. This oil waschromatographed on silica gel (125 g), eluting with chloroform. A paleyellow semisolid (liquid crystalline at room temperature) resulted. Theyield of the desired product,5-octyl-2-(4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenyl)pyrimidine,Compound 2, Table 1, was 6.4 g.

EXAMPLE 16

A 100 mL 3-neck flask fitted with a magnetic stir bar, septum, stopper,and water cooled condenser connected to a nitrogen bubbler was chargedwith 60% sodium hydride/mineral oil (0.8 g, 0.02 moles), toluene (15mL), and dimethyl formamide (15 mL). With vigorous stirring,5-octyl-2-(4-hydroxyphenyl)pyrimidine (3.76 g, 0.0132 moles) was addedslowly to control the hydrogen evolution. The resulting mixture wasstirred at room temperature for 30 minutes. Then,1,1-dihydroperfluoro-2-(butoxyethoxy)ethyl triflate (7.47 g, 0.0132moles, prepared as in Example 3) was added and the solution was heatedto reflux. After 1 hour, the reaction mixture was cooled to roomtemperature. The contents of the flask were poured into a separatoryfunnel containing water (50 mL). The resulting layers were separated andthe aqueous layer was extracted twice with toluene (20 mL). The combinedorganic layers were then washed three times with water, treated withsilica gel (5 g) for one hour, and filtered. After solvent removal onrotary evaporator, a light brown oil resulted. This oil waschromatographed on silica gel (125 g), eluting with chloroform. A paleyellow semisolid (liquid crystalline at room temperature) resulted. Theyield of the desired product,5-octyl-2-(4-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxy)phenyl)pyrimidine,Compound 3, Table 1, was 4.7 g.

EXAMPLE 17

Product was prepared as in Example 16 except 0.585 g sodium hydride, 80%dispersion in oil and 11.0 g 1,1-dihydroperfluoro-2-butoxyethoxyethyltriflate were used and 5.0 g 5-hexyl-2-(4-hydroxyphenyl)pyrimidine wassubstituted for the 5-octyl-2-(4-hydroxyphenyl)pyrimidine. The resultingproduct,5-hexyl-2-(4-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxy)phenyl)pyrimidine,is Compound 4, Table 1.

EXAMPLE 18

A 50 mL flask was charged with 60% sodium hydride in mineral oil (0.2 g,0.004 moles), toluene (10 mL), N,N-dimethylformamide (10 mL) and5-octyl-2-(4'-hydroxybiphenyl)pyrimidine (0.00277 moles, prepared as inExample 4) under an atmosphere of dry nitrogen. The mixture was stirredat room temperature for 1.5 hours. 1,1-Dihydroheptafluoro-2-ethoxyethyltriflate (0.96 g, 0.00277 moles) was then added, and the mixture washeated to 100° C. for 1.5 hours. After cooling to room temperature, thecontents of the flask were poured into a separatory funnel containingwater (60 mL) and toluene (20 mL). The layers were separated and theaqueous layer was extracted twice with 20 mL of toluene. The combinedorganic layers were washed three times with 30 mL of water, dried withanhydrous sodium sulfate, and filtered. The solvent was removed underreduced pressure. The resulting brown solid was recrystallized fromethanol, and then flash chromatographed on silica gel, eluting withchloroform to yield 0.58 g of white solid,5-octyl-2-(4'-(1,1-dihydroheptafluoro-2-ethoxyethoxy)biphenyl)pyrimidine (Compound 5, Table 1).

EXAMPLE 19

5-Octyl-2-(4'-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxybiphenyl)pyrimidinewas prepared as described in Example 18, except that1,1-dihydroperfluoro-2-(2-1-butoxyethoxy)ethyl triflate (1.6 g, 0.00277moles) was used in place of 1,1-dihydroheptafluoro-2-ethoxyethyltriflate, to yield 0.4 g of5-octyl-2-(4'-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxybiphenyl)pyrimidine(Compound 6, Table 1).

EXAMPLE 20

4-Decyloxybenzoic acid (0.45 g, 0.0016 moles) and4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol (0.5 g, 0.0016 moles,prepared as in Example 5) were dissolved in dichloromethane (25 mL).1,3-dicyclohexylcarbodiimide (0.35 g, 0.0017 moles) was added to thereaction mixture, followed by 4-(N,N-dimethylamino)pyridine (0.05 g,0.0004 moles). The resultant mixture was stirred at room temperatureunder nitrogen for 18 hours. The precipitated urea was removed from theproduct solution by filtration, and the filtrate was concentrated on arotary evaporator at reduced pressure. The crude solid was purified byrecrystallization from ethanol, followed by flash chromatography onsilica gel, eluting with chloroform, to yield 0.12 g of the desiredproduct, Compound 7, in Table 1.

EXAMPLES 21-31

In Examples 21-31, Compounds 8-20 of Table 1, respectively, wereprepared as in Example 20, except the precursor compounds indicatedbelow were substituted for the 4-decyloxybenzoic acid and the4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol.

Example 21, compound 8, was prepared from 3-chloro-4-octyloxybenzoicacid and 4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol (Example 5).

Example 22, compound 9, was prepared from 3-chloro-4-octyloxybenzoicacid and 4-(1,1-dihydroperfluoro-2-(butoxyethoxy)ethoxy)phenol (Example6).

Example 23, compound 10, was prepared from 6-(4-methylhexyloxy)nicotinicacid and 4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol (Example 5).This product was liquid at room temperature, thus it was notrecrystallized, and was simply purified by chromatography.

Example 24, compound 11, was prepared from 6-(4-methylhexyloxy)nicotinicacid and 4-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxy)phenol(Example 6). This product was liquid at room temperature, thus it wasnot recrystallized, and was simply purified by chromatography.

Example 25, compound 12, was prepared from octyloxybenzoic acid and6-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-2-hydroxynapthalene (Example9).

Example 26, compound 13, was prepared from decyloxybenzoic acid and6-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-2-hydroxynapthalene (Example9).

Example 27, compound 14, was prepared from decyloxybenzoic acid and6-(1,1-dihydroperfluoro-2-(2-butoxyethoxy)ethoxy)-2-hydroxynapthalene(Example 10).

Example 28, compound 15, was prepared from octyloxybenzoic acid and4'-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-4-hydroxybiphenyl (Example7).

Example 29, compound 16, was prepared from decyloxybenzoic acid and4'-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-4-hydroxybiphenyl (Example7).

Example 30, compound 17, was prepared from decyloxybenzoic acid and4'-(1,1-dihydroprefluoro-2-(2-butoxyethoxy)ethoxy)-4-hydroxybiphenyl(Example 8).

Example 31, compound 18, was prepared from4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)benzoic acid (Example 11) andhydroquinone mono-trans-4-pentylcyclohexanecarboxylate.

EXAMPLE 32

2,3-Dicyano-4-octyloxyphenol (0.8 g, 0.0030 mole, Example 12),1,1-dihydroheptafluoro-2-ethoxyethoxy)benzoic acid (1.0 g, 0.0030 mole,Example 11) and dichloromethane (50 mL) were placed into a 100 mL roundbottom flask under a dry nitrogen atmosphere.1,3-Dicyclohexylcarbodiimide (0.64 g, 0.0031 mole) and a few crystals of4-(N,N-dimethylamino)pyridine were added with stirring. Stirring wascontinued for four hours at room temperature. The resulting mixture wasthen filtered to remove precipitated urea that had formed. In aseparatory funnel, the clear filtrate was washed with dilutehydrochloric acid, dilute potassium carbonate and water. After dryingwith anhydrous magnesium sulfate, the solution was again filtered andthe solvent was removed on a rotary evaporator to yield a white solid.The solid was then flash chromatographed on silica gel (80 g), elutingwith dichloromethane to isolate the desired product,2,3-dicyano-4-octyloxyphenyl-4-(1,1-dihydroheptafluoroethylethoxy)benzoate,Compound 19, Table 1.

EXAMPLE 33

2,3-Difluoro-4-octyloxyphenol (0.92 g, 0.0036 mole, Example 13),4-(1,1-dihydroheptafluoroethylethyoxy)benzoic acid (1.2 g, 0.0036 mole,Example 11) and dichloromethane (60 mL) were placed into a 100 mL roundbottom flask under a dry nitrogen atmosphere.1,3-Dicyclohexylcarbodiimide (0.77 g, 0.0037 mole) and a few crystals of4-(N,N-dimethylamino)pyridine were added with stirring. Stirring wascontinued for four hours at room temperature. The resulting mixture wasthen filtered to remove precipitated urea that had formed. In aseparatory funnel, the clear filtrate was washed with dilutehydrochloric acid, dilute potassium carbonate and water. After dryingwith anhydrous magnesium sulfate, the solution was again filtered andthe solvent was removed on a rotary evaporator to yield a white solid.The solid was then flash chromatographed on silica gel (80 g), elutingwith dichloromethane to isolate the desired product,2,3-difluoro-4-octyloxyphenyl-4-(1,1-dihydroheptafluoroethoxyethoxy)benzoate(1.2 g), Compound 20, Table 1.

COMPARATIVE EXAMPLES 1-5

In Comparative Example 1, Compound C1, Table 1, was prepared using theprocedure used to prepare Compound 7, except4-(1,1-dihydroperfluorobutoxy)phenol was used in place of4-(1,1-dihydroheptafluoro-2-ethoxyethoxy)phenol.

In Comparative Example 2, Compound C2, Table 1, was prepared using theprocedure used to prepare Compound 10, except4-(1,1-dihydroheptafluorobutoxy)phenol was used in place of4-(1,1-dihydro-heptafluoro-2-ethoxyethoxy)phenol.

In Comparative Example 3, Compound C3, Table 1, was prepared using theprocedure used to prepare Compound 13, except6-(1,1-dihydroperfluorobutoxy)-2-naphthol was used in place of6-(1,1-dihydroheptafluoro-2-ethoxyethoxy)-2-hydroxynaphthalene.

In Comparative Example 4, Compound C4, Table 1, was prepared using theprocedure of Example 15 except 1,1-dihydroperfluorobutyl triflate wassubstituted for 1,1-dihydroheptafluoro-2-ethoxyethyl triflate.

In Comparative Example 5, Compound C5, Table 1, was prepared using theprocedure of Example 15 except 1,1-dihydroperfluorohexyl triflate wassubstituted for 1,1-dihydroheptafluoro-2-ethoxyethyl triflate.

                                      TABLE 1                                     __________________________________________________________________________    Compound                                                                            Structure                                                               __________________________________________________________________________     1                                                                                   ##STR16##                                                               2                                                                                   ##STR17##                                                               3                                                                                   ##STR18##                                                               4                                                                                   ##STR19##                                                               5                                                                                   ##STR20##                                                               6                                                                                   ##STR21##                                                               7                                                                                   ##STR22##                                                               8                                                                                   ##STR23##                                                               9                                                                                   ##STR24##                                                              10                                                                                   ##STR25##                                                              11                                                                                   ##STR26##                                                              12                                                                                   ##STR27##                                                              13                                                                                   ##STR28##                                                              14                                                                                   ##STR29##                                                              15                                                                                   ##STR30##                                                              16                                                                                   ##STR31##                                                              17                                                                                   ##STR32##                                                              18                                                                                   ##STR33##                                                              19                                                                                   ##STR34##                                                              20                                                                                   ##STR35##                                                              C1                                                                                   ##STR36##                                                              C2                                                                                   ##STR37##                                                              C3                                                                                   ##STR38##                                                              C4                                                                                   ##STR39##                                                              C5                                                                                   ##STR40##                                                              __________________________________________________________________________

The compounds of Table 1 were evaluated for transition temperatures byoptical observation of material phase changes using a Linkam TMH600 hotstage and a Zeiss polarizing microscope. The transition temperature(°C.), upon cooling from the isotropic state (I) to the crystallinestate (K), are set forth in Table 2.

                  TABLE 2                                                         ______________________________________                                        Compound                                                                      No.      I to SmA to SmC    to SmE to M  to K                                 ______________________________________                                         1        83                        1                                          2        67       26                     7                                    3        74       47                    -5                                    4        60       22              -15                                         5       200      151              66    64                                    6       208      158       145    51    42                                    7       72.8     63.3                   37.7                                  Cl       87       61                    42                                    8                                       36                                    9        65                       37                                         10       (virtual                        22                                            SmA at 6                                                                      on rapid                                                                      cooling)                                                             C2        43                             30                                   11        27                             ←43                             12       131       62        50          36                                   13       128       81                    44                                   C3       137       91                    44                                   14       148       97              51    44                                   15       222      145       105    85                                         16       186      136       121    105                                        17       189      158                    92                                   18       189      113              97    83                                   19                                       106                                  20                                       63                                   ______________________________________                                    

As can be in comparing Compound 6 to Compound C1, Compound 9 to CompoundC2 and Compound 12 to Compound C3, the compounds of the presentinvention having perfluoroether terminal portions have lower transitiontemperatures for I to SmA than do similar compounds not having the ethergroup in the perfluoro terminal portion.

That the compounds of the present invention have lower transitiontemperatures, particularly with regard to the Smectic A and Smectic Cmesophases, is further shown in FIGS. 1 and 2 where the phases weredetermined using DSC and optical microscopy, respectively.

In FIG. 1:

A is the Smectic A phase for Compound C4,

A' is the Smectic C phase for Compound C4,

B is the Smectic A phase for Compound 2,

B' is the Smectic C phase for Compound 2,

C is the Smectic A phase for Compound C5,

C' is the Smectic C phase for Compound C5,

D is the Smectic A phase for Compound 3, and

D' is the Smectic C phase for Compound 3.

In FIG. 2:

E is the Smectic A phase for Compound C4,

E' is the Smectic C phase for Compound C4,

F is the Smectic A phase for Compound 2,

F' is the Smectic C phase for Compound 2,

G is the Smectic A phase for Compound C5,

G' is the Smectic C phase for Compound C5,

H is the Smectic A phase for Compound 3, and

H' is the Smectic C phase for Compound 3.

EXAMPLE 34 AND COMPARATIVE EXAMPLE C6

In Example 34, a liquid crystal mixture was prepared containing

    __________________________________________________________________________    5   parts                                                                              ##STR41##                                                            1.67                                                                              parts                                                                              ##STR42##                                                            1.67                                                                              parts                                                                              ##STR43##                                                            1.66                                                                              parts                                                                              ##STR44##                                                            __________________________________________________________________________

The mixture was evaluated for transition temperatures by opticalobservation of material phase changes using a Linkam TMH600 hot stageand a Zeiss polarizing microscope. The results are set froth in Table 3.

In Comparative Example 6, a mixture was prepared as in Example 34 exceptthe liquid crystal material having the perfluoroether terminal portionwas omitted. The mixture was evaluated for transition temperatures as inExample 34. The results are set forth in Table 3.

                  TABLE 3                                                         ______________________________________                                        Transition Temperatures (°C.)                                          Example  I to SmA    SmA to SmC SmC to K                                      ______________________________________                                        34        89         59         23                                            C6       111         84         69                                            ______________________________________                                    

As can be seen from the data in Table 3, addition of the liquid crystalmaterial having the perfluoroether terminal portion significantlylowered the transition temperatures.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope ofthe invention.

What is claimed is:
 1. An achiral fluorine-containing liquid crystalcompound of the general formula I: ##STR45## where M, N, and P are eachindependently ##STR46## a, b, and c are each independently zero or aninteger of from 1 to 3 with the proviso that the sum of a+b+c be atleast 2;each A and B are non-directionally and independently a covalentbond, ##STR47## each X, Y, and Z are independently --H, --Cl, --F, --Br,--I, --OH, --OCH₃, --CN, or --NO₂ ; each 1, m, and n are independentlyzero or an integer of 1 to 4, D is ##STR48## and q and q' areindependently 1 to 20, and R can be straight chain or branched; andR_(f) is (C_(x) F_(2x) O)_(z) C_(y) F_(2y+1) where x is independently 1to 10 for each C_(x) F_(2x) O group, y is 1 to 10 and z is 1 to
 6. 2. Acompound according to claim 1 wherein said compound can be representedby the formula ##STR49## where d is 5 to 10, x is independently 1 to 3for each C_(x) F_(2x) O group, y is 1 to 4 and z is 1 to
 3. 3. Acompound according to claim 1 wherein said compound can be representedby the formula ##STR50## where t is 6, 8 or
 10. 4. A compound accordingto claim 1 wherein said compound can be represented by the formula##STR51## where t is 6, 8 or
 10. 5. A compound according to claim 1wherein said compound can be represented by the formula ##STR52## wheret is 6, 8 or
 10. 6. A compound according to claim 1 wherein saidcompound can be represented by the formula ##STR53##
 7. A compoundaccording to claim 1 wherein said compound can be represented by theformula ##STR54## where t is 6, 8 or
 10. 8. A compound according toclaim 1 wherein said compound can be represented by the formula##STR55## where t is 6, 8 or
 10. 9. A compound according to claim 1wherein said compound can be represented by the formula ##STR56##
 10. Acompound according to claim 1 wherein said compound can be representedby the formula ##STR57##
 11. A compound according to claim 1 whereinR_(f) is --CF₂ OCF₂ CF₂ OC₄ F₉.
 12. Liquid crystal mixtures comprisingat least one compound according to claim 1 and at least one chiralliquid crystal compound, said chiral liquid crystal compound beingpresent in an amount sufficient to provide the mixture withferroelectric properties.
 13. A liquid crystal display device containingsaid compound of claim 1 wherein said compound has a smectic mesophase.